Insulin, a hormone, is used to regulate carbohydrate and fat metabolism in the body. Insulin causes cells to take up glucose from the blood and store it as glycogen in the liver and muscle. This hormone stops the body from using fat as an energy source by inhibiting the release of glucagons. Without insulin the body fails to take glucose into the bodies cells and in turns uses fat as an energy source. It also has several other anabolic effects throughout the body.
Diabetes mellitus results...

A pivoted catch designed to fall into a notch on a ratchet wheel so as to allow movement in only one direction (e.g. on a windlass or in a clock mechanism), or alternatively to move the wheel in one direction.